Methods and devices for spinal screw insertion

ABSTRACT

Surgical instruments and methods for delivering bone anchor assemblies into bone are disclosed herein. Use of these anchors or instruments can eliminate one or more of the steps in a conventional bone anchor installation procedure, improving surgical efficiency and safety. In general, a surgical instrument can include a handle assembly having an elongate shaft extending distally therefrom. The handle assembly can be configured to axially translate a stylet extending therethrough relative to a bone anchor assembly coupled to the elongate shaft, and it can be configured to move the stylet proximally in response to distal advancement of a bone anchor assembly into bone. The surgical instruments can include various mechanisms for adjusting the position of the stylet.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/848,609, filed Dec. 20, 2017 and entitled “Methods and Devices forSpinal Screw Insertion,” which is a divisional of U.S. application Ser.No. 14/450,952, filed on Aug. 4, 2014 and entitled “Methods and Devicesfor Spinal Screw Insertion,” which are hereby incorporated by referencein their entireties.

FIELD

Bone anchors and associated instrumentation and methods are disclosedherein.

BACKGROUND

Bone anchors can be used in orthopedic surgery to fix bone duringhealing, fusion, or other processes. In spinal surgery, for example,bone anchors can be used to secure a spinal fixation element to one ormore vertebrae to rigidly or dynamically stabilize the spine.

In a conventional procedure for coupling a bone anchor to bone, accessto the bone is obtained, for example by forming a skin incision andresecting soft tissue disposed over the bone or by using aminimally-invasive technique. An insertion needle with a stylet disposedtherein, sometimes referred to as a Jamshidi needle, is then driven intothe bone to establish the trajectory for a bone opening. Next, thestylet is removed and a guidewire is inserted through the needle. Theneedle is then withdrawn over the guidewire, leaving the guidewire inplace. A cannulated tap is then advanced over the guidewire and driveninto the bone to enlarge the bone opening into a pilot hole for the boneanchor. Thereafter, the tap is withdrawn over the guidewire, againleaving the guidewire in place within the bone opening. A cannulatedbone anchor is then advanced over the guidewire and driven into the boneopening. Finally, the guidewire is removed and one or more fixationelements are coupled to the bone anchor.

The conventional procedure detailed above suffers from a number ofdisadvantages. For example, the process involves several steps which canbe time-consuming and cumbersome, particularly where a number of boneanchors are being installed. In addition, many of these steps (e.g.,advancing the needle, advancing the guidewire, advancing the tap, andadvancing the bone anchor) are done with fluoroscopic guidance toconfirm the correct trajectory and insertion depth. With each additionalstep, the radiation exposure to the patient and surgical team increases,potentially causing dangerous complications or negative long-term healtheffects. The steps of removing the needle and removing the tap can alsocause the guidewire to dislodge from the bone opening, requiring theprocess to be started anew. Further still, advancing the anchor oradvancing the tap can inadvertently cause the guidewire to advancewithin the bone opening, potentially damaging delicate anatomicalstructures disposed in proximity to the bone. Advancing the anchor oradvancing the tap can also cause the guidewire to become kinked, makingremoval of the guidewire very difficult. Accordingly, a need exists forimproved bone anchors and associated instrumentation and methods.

SUMMARY

Various surgical instruments and methods are disclosed herein forimplanting a bone anchor into bone. In one embodiment, a surgicalinstrument for driving a bone anchor assembly into bone is provided andincludes an elongate shaft having a distal tip configured to couple to abone anchor assembly, a handle assembly coupled to a proximal end of theshaft, and a stylet extending through an inner lumen of the handleassembly and the elongate shaft. The surgical instrument can furtherinclude a carrier disposed within the handle assembly, with the carrierbeing configured to non-rotatably translate relative to the elongateshaft in a proximal direction through the handle assembly to move thestylet proximally when the elongate shaft is rotated in order to drive abone anchor assembly into bone.

The handle assembly can include a first and a second handles rotatablycoupled to one another. Rotation of the first handle while the secondhandle is held stationary can cause the carrier to non-rotatablytranslate axially relative to the elongate shaft. Rotation of the secondhandle while the first handle is held stationary can cause the carrierto rotatably translate relative to the first handle. In someembodiments, the first handle can be positioned distal to the secondhandle. The surgical instrument can further include a stylet holdercoupled to the carrier and releasably engaged to the stylet. The styletholder can be releasably engaged with the carrier and can allow axialtranslation of the stylet when the stylet holder is in a first positionrelative to the carrier, and can prevent axial translation of the styletwhen the stylet holder is in a second position relative to the carrier.The surgical instrument can further include a bone anchor assemblymatable to the distal tip of the elongate shaft and having threadsformed thereon that define an insertion rate of the bone anchor assemblyinto bone. The carrier can be configured to translate within the handleassembly at a rate that is equal to the insertion rate of the boneanchor assembly.

In some embodiments, a surgical instrument for driving a bone anchorassembly into bone can include an elongate shaft having proximal anddistal ends, a mating feature formed on the distal end that isconfigured to mate to a bone anchor assembly, and an inner lumenextending through the elongate shaft. A stylet can extend through theinner lumen of the elongate shaft. The surgical instrument can alsoinclude a proximal handle configured to rotate the elongate shaft todrive a bone anchor assembly coupled to the mating feature on the distalend of the elongate body into bone. In addition, the surgical instrumentcan include a distal handle rotatable relative to the proximal handle.The surgical instrument can further include a carrier threadablydisposed within the handle assembly and configured to move axiallyrelative to the elongate shaft in response to rotation of one of theproximal and distal handles relative to the other one of the proximaland distal handles in order to cause the stylet to translate axiallyrelative to the elongate shaft.

In one embodiment, rotation of the proximal handle while the distalhandle is held stationary can cause rotation of the elongate shaft, androtation and axial translation of the carrier within the handleassembly. Conversely, rotation of the distal handle while the proximalhandle is held stationary can cause the carrier to translate axiallywithin the handle assembly without rotating the elongate shaft. Incertain embodiments, the proximal handle can be mated to the proximalend of the elongate shaft, and the distal handle can be rotatablydisposed about a proximal portion of the elongate shaft at a locationdistal to the proximal handle. The carrier can be threadably coupled tothreads formed within the distal handle and the stylet can be integrallyformed on and can extend distally from the carrier. Alternatively or inaddition, the stylet can be removably mated to the carrier by a matingelement.

In certain embodiments, the surgical instrument can include a styletholder disposed within the handle assembly that can allow the stylet toextend therethrough. The stylet holder can have a first position, inwhich the stylet is freely slidable relative to the stylet holder, and asecond position in which the stylet holder rigidly engages the stylet toprevent movement of the stylet relative to the stylet holder. The styletholder can be configured to be advanced into the carrier to cause thestylet holder to move from the first position to the second position.The stylet holder can include a clamping feature that is compressed bythe carrier in the second position to cause the clamping feature torigidly engage the stylet.

In other aspects, the elongate shaft of the surgical instrument caninclude a proximal portion with one or more slots, with the proximalportion extending through the distal handle and having a proximal endmated to the proximal handle. The carrier can be slidably disposedwithin the proximal portion, and the carrier can be non-rotatablerelative to the proximal portion such that the carrier and the elongateshaft rotate together. The carrier can include one or more threadedfeatures that extend through the one or more slots. The one or moreslots can allow translation while preventing rotation of the carrierwithin the elongate shaft.

The surgical instrument can include other components, such as aprotective sleeve removably disposed around the elongate shaft, and/or apositioning handle coupled to a proximal end of the stylet that isconfigured to adjust a length of stylet that extends from a bone anchorassembly coupled to the distal end of the elongate shaft. Thepositioning handle can include a tool feature for engaging a styletholder disposed within the handle assembly and having the styletextending therethrough. The tool feature can be configured to advancethe stylet holder into the carrier to cause the stylet holder to movefrom a first position to a second position, wherein the second positionlocks the stylet to the stylet holder. The positioning handle caninclude an outer housing encompassing at least a part of a positioningfeature that secures the proximal end of the stylet to the positioninghandle. The positioning feature can include a push button thatreleasably engages an engagement position along the outer housing. Thepositioning feature can be configured to move with the stylet relativeto the outer housing when the push button is disengaged from theengagement position.

In some embodiments, a surgical instrument for driving a bone anchorassembly into bone can include an elongate shaft having proximal anddistal ends, a mating feature formed on the distal end and configured tomate to a bone anchor assembly, an inner lumen extending through theelongate shaft, and a handle assembly coupled to the elongate shaft. Thehandle assembly can include a distal handle coupled to the proximal endof the elongate shaft and it can be configured to rotate the elongateshaft to drive a bone anchor assembly coupled to the mating feature onthe distal end of the elongate body into bone. The handle assembly canfurther include a proximal handle threadably coupled to the distalhandle and coupled to a proximal end of a stylet that extends throughthe inner lumen of the elongate shaft, with the proximal handle beingrotatable relative to the distal handle in order to cause the stylet toaxially translate relative to the elongate shaft.

In some embodiments, a method of delivering a bone anchor assembly isprovided. The method can include coupling an engagement portion on ashaft of a driver to a corresponding engagement portion on a bone anchorassembly. The method can also include rotating a second handle of thedriver while holding a first handle of the driver stationary to cause acarrier disposed within the driver to translate a stylet relative to thebone anchor assembly. The method can further include rotating a firsthandle of the driver while holding a second handle of the driverstationary to cause the shaft to rotate and advance the bone anchorassembly along the stylet. When the first handle is rotated while thesecond handle is held stationary, the carrier can be caused to translateaxially within the driver to move the stylet axially relative to theelongate shaft.

The present disclosure further provides devices and methods as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is an exploded perspective view of a prior art bone anchorassembly;

FIG. 1B is a sectional view of the prior art bone anchor assembly ofFIG. 1A;

FIG. 2A is an exploded perspective view of one embodiment of a surgicalinstrument having a stylet that can be coupled to a carrier, the carrierand stylet can be axially translated as a result of rotating proximaland distal handles relative to one another;

FIG. 2B is a cross-sectional view of the surgical instrument of FIG. 2Awith a bone anchor assembly coupled to a distal end of an elongate shaftof the surgical instrument;

FIG. 3 is a cross-sectional view of another embodiment of a surgicalinstrument having a stylet integrated with and extending distally from acarrier;

FIG. 4 is a cross-sectional view of yet another embodiment of a surgicalinstrument having a stylet threadably engaged with a carrier;

FIG. 5A is an exploded perspective view of a surgical instrument havingproximal and distal handles and a stylet holder for carrying a stylet,according to another embodiment;

FIG. 5B is a side view of the surgical instrument of FIG. 5A with a boneanchor assembly coupled to a distal end of an elongate shaft of thesurgical instrument;

FIG. 5C is a cross-sectional view of the surgical instrument and boneanchor assembly of FIG. 5B;

FIG. 5D is an exploded perspective view of the surgical instrument shownin FIGS. 5A-5C having a stylet with a positioning handle;

FIG. 5E is a side view of the positioning handle of FIG. 5D showing awindow in an outer body of the positioning handle revealing a marking;

FIG. 5F is a top view of the positioning handle of FIG. 5D showing apush button for adjusting a position of a stylet;

FIG. 5G is a cross-sectional view of the positioning handle of FIG. 5Dshowing a positioning feature within the outer body of the positioninghandle.

FIG. 6A is a cross-sectional view of another embodiment of a surgicalinstrument in a retracted position having a stylet coupled to a proximalhandle, which can allow the stylet to be axially translated as a resultof rotating the proximal handle relative to a distal handle of thesurgical instrument;

FIG. 6B is a cross-sectional view of the surgical instrument of FIG. 6Ain an extended position;

FIG. 7 is a cross-sectional view of a protective sleeve positioned overa part of the elongate shaft of the surgical instrument shown in FIGS.6A and 6B;

FIG. 8 is a cross-sectional view of a protective sleeve positioned overa part of the elongate shaft of surgical instrument shown in FIG. 4 ;

FIGS. 9A-9C schematically illustrate a method of using the surgicalinstrument of FIGS. 2A and 2B to drive a bone anchor assembly into bone;and

FIG. 10A-10D schematically illustrate a method of using the positioninghandle and surgical instrument of FIGS. 5A-5G to drive a bone anchorassembly into bone.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

Methods and devices for inserting bone anchor assemblies into bone areprovided herein. Use of these anchors or instruments can eliminate oneor more of the steps in a conventional bone anchor installationprocedure, improving surgical efficiency and safety. In general,surgical insertion devices are provided that include a proximal handleand a distal handle, with the proximal handle configured to control themovement of an elongate shaft of the device and the distal handleconfigured to control the movement of a guidewire or stylet extendingthrough the device. For example, rotation of the distal handle relativeto the proximal handle can cause the stylet to axially translate in aproximal or distal direction relative to the elongate shaft. Inaddition, rotation of the proximal handle relative to the distal handlecan cause the elongate shaft to rotate, which can assist with driving abone anchor assembly coupled to a distal end of the elongate shaft intobone. We note that the terms guidewire and stylet are usedinterchangeably herein, and any configuration of a guidewire or styletcan be used with the various instruments and methods disclosed herein.

Prior Art Bone Anchor Assembly

FIGS. 1A-1B illustrate one embodiment a prior art bone anchor assembly10 that includes a bone anchor 12, a receiver member 14 for receiving aspinal fixation element, such as a spinal rod 22, to be coupled to thebone anchor 12, and a closure mechanism 16 to capture a spinal fixationelement within the receiver member 14 and fix the spinal fixationelement with respect to the receiver member 14. The bone anchor 12includes a proximal head 18 and a distal shaft 20 configured to engagebone. The receiver member 14 has a proximal end 26 having a pair ofspaced apart arms 28A, 28B defining a recess 30 therebetween and adistal end 32 having a distal end surface 34 defining an opening throughwhich at least a portion of the bone anchor 12 extends. The closuremechanism 16 can be positionable between and can engage the arms 28A,28B to capture a spinal fixation element, e.g., a spinal rod 22, withinthe receiver member 14 and fix the spinal fixation element with respectto the receiver member 14.

The proximal head 18 of the bone anchor 12 is generally in the shape ofa truncated sphere having a planar proximal surface 36 and anapproximately spherically-shaped distal surface 38. The illustrated boneanchor assembly is a polyaxial bone screw designed for posteriorimplantation in the pedicle or lateral mass of a vertebra. The proximalhead 18 of the bone anchor 12 engages the distal end 32 of the receivermember 14 in a ball and socket like arrangement in which the proximalhead 18 and the distal shaft 20 can pivot relative to the receivermember 14. The distal surface 38 of the proximal head 18 of the boneanchor 12 and a mating surface within the distal end 32 of the receivermember 14 can have any shape that facilitates this arrangement,including, for example, spherical (as illustrated), toroidal, conical,frustoconical, and any combinations of these shapes.

The distal shaft 20 of the bone anchor 12 can be configured to engagebone and, in the illustrated embodiment, includes an external boneengaging thread 40. The thread form for the distal shaft 20, includingthe number of threads, the pitch, the major and minor diameters, and thethread shape, can be selected to facilitate connection with bone.Exemplary thread forms are disclosed in U.S. Patent ApplicationPublication No. 2011/0288599, filed on May 18, 2011, and in U.S. PatentApplication Publication No. 2013/0053901, filed on Aug. 22, 2012, bothof which are hereby incorporated by reference herein. While a threadeddistal shaft 20 is shown, the distal shaft can have other structures forengaging bone, including a hook. The distal shaft 20 of the bone anchor12 can be cannulated, having a central passage or inner lumen 72extending the length of the bone anchor to facilitate delivery of thebone anchor over a guidewire or stylet in, for example,minimally-invasive procedures. Other components of the bone anchorassembly 10, including, for example, the closure mechanism 16, thereceiver member 14, and the compression member 60 (discussed below), canbe cannulated or otherwise have an opening to permit delivery over aguidewire or stylet. The distal shaft 20 can also include one or moresidewall openings or fenestrations that communicate with the inner lumen72 to permit bone in-growth or to permit the dispensing of bone cementor other materials through the bone anchor 12. The sidewall openings canextend radially from the inner lumen 72 through the sidewall of thedistal shaft 20. Exemplary systems for delivering bone cement to thebone anchor assembly 10 and alternative bone anchor configurations forfacilitating cement delivery are described in U.S. Patent ApplicationPublication No. 2010/0114174, filed on Oct. 29, 2009, which is herebyincorporated by reference herein. The distal shaft 20 of the bone anchor12 can also be coated with materials to permit bone growth, such as, forexample, hydroxyapatite, and the bone anchor assembly 10 can be coatedpartially or entirely with anti-infective materials, such as, forexample, tryclosan.

The receiver member 14, which couples to the bone anchor 12, includes apair of spaced apart arms 28A, 28B at the proximal end 26 defining aU-shaped recess 30 therebetween for receiving a spinal fixation element,e.g., a spinal rod 22. Each of the arms 28A, 28B can extend from thedistal end 32 of the receiver member 14 to a free end. The outersurfaces of each of the arms 28A, 28B can include a feature, such as arecess, dimple, notch, projection, or the like, to facilitate connectionof the receiver member 14 to instruments. For example, the outer surfaceof each arm 28A, 28B can include an arcuate groove at the respectivefree end of the arms. Such grooves are described in more detail in U.S.Pat. No. 7,179,261, issued on Feb. 20, 2007, which is herebyincorporated by reference herein.

The distal end 32 of the receiver member 14 includes a distal endsurface 34 which is generally annular in shape defining a circularopening through which at least a portion of the bone anchor 12 extends.For example, the distal shaft 20 of the bone anchor 12 can extendthrough the opening.

The bone anchor 12 can be selectively fixed relative to the receivermember 14. Prior to fixation, the bone anchor 12 is movable relative tothe receiver member 14 within a cone of angulation generally defined bythe geometry of the distal end 32 of the receiver member and theproximal head 18 of the bone anchor 12. The bone anchor 10 can be afavored angle screw, for example as disclosed in U.S. Pat. No.6,974,460, issued on Dec. 13, 2005, and in U.S. Pat. No. 6,736,820,issued on May 18, 2004, both of which are hereby incorporated byreference herein. Alternatively, the bone anchor assembly can be aconventional (non-biased) polyaxial screw in which the bone anchorpivots in the same amount in every direction.

The spinal fixation element, e.g., the spinal rod 22, can eitherdirectly contact the proximal head 18 of the bone anchor 12 or cancontact an intermediate element, e.g., a compression member 60. Thecompression member 60 can be positioned within the receiver member 14and interposed between the spinal rod 22 and the proximal head 18 of thebone anchor 12 to compress the distal outer surface 38 of the proximalhead 18 into direct, fixed engagement with the distal inner surface ofthe receiver member 14. The compression member 60 can include a pair ofspaced apart arms 62A and 62B defining a U-shaped seat 64 for receivingthe spinal rod 22 and a distal surface 66 for engaging the proximal head18 of the bone anchor 12.

The proximal end 26 of the receiver member 14 can be configured toreceive a closure mechanism 16 positionable between and engaging thearms 28A, 28B of the receiver member 14. The closure mechanism 16 can beconfigured to capture a spinal fixation element, e.g., a spinal rod 22,within the receiver member 14, to fix the spinal rod 22 relative to thereceiver member 14, and to fix the bone anchor 12 relative to thereceiver member 14. The closure mechanism 16 can be a single set screwhaving an outer thread for engaging an inner thread 42 provided on thearms 28A, 28B of the receiver member 14. In other embodiments, however,the closure mechanism 16 can include an outer set screw operable to acton the compression member 60 and an inner set screw operable to act onthe rod 22.

The bone anchor assembly 10 can be used with a spinal fixation elementsuch as rigid spinal rod 22. Alternatively, the spinal fixation elementcan be a dynamic stabilization member, such as a flexible or selectivelyflexible member, that allows controlled mobility between theinstrumented vertebrae.

In use, the bone anchor assembly 10 can be assembled such that thedistal shaft 20 extends through the opening in the distal end 32 of thereceiver member 14 and the proximal head 18 of the bone anchor 12 isreceived in the distal end 32 of the receiver member 14. The compressionmember 60 can be positioned within the receiver member 14 such that thearms 62A, 62B of the compression member are aligned with the arms 28A,28B of the receiver member 14 and the lower surface of the compressionmember 14 is in contact with the proximal head 18 of the bone anchor 12.A driver tool can extend through the compression member 60 and can befitted with the bone anchor 12 to drive the bone anchor 12 into bone. Aspinal fixation element, e.g., the spinal rod 22, can be located in therecess 30 of the receiver member 14. The closure mechanism 16 can beengaged with the inner thread 42 provided on the arms 28A, 28B of thereceiver member 14. A torsional force can be applied to the closuremechanism 16 to move it within the recess 30 so as to force the spinalrod 22 into engagement with the compression member 60 and to in turnforce the compression member 60 onto the proximal head 18 of the boneanchor 12, thereby fixing the spinal rod 22 relative to the receivermember 14 and locking the angular position of the bone anchor 12relative to the receiver member 14.

The surgical instruments disclosed herein can be configured to operatein conjunction with bone anchor assemblies of the type described aboveor other types known in the art. As indicated above, it will beappreciated that the bone anchor assembly 200 can be a monoaxial screw,a polyaxial screw, a uniplanar screw, a bone hook, a favored-anglescrew, and/or any of a variety of other bone anchor types known in theart. Further information on favored-angle screws can be found in U.S.patent application Ser. No. 13/648,184, filed on Oct. 9, 2012, which ishereby incorporated by reference herein.

Insertion Instruments

In general, various insertion instruments are provided for driving abone anchor assembly into bone. The insertion instruments generallyinclude a handle assembly and an elongate shaft extending distallytherefrom for coupling to a bone anchor assembly. The instruments areconfigured to receive a stylet therethrough and the handle assembly isconfigured to control positioning of the stylet. In particular, thehandle assembly can be configured to allow for adjustment of an axialposition of the stylet relative to a bone anchor assembly coupled to theelongate shaft. The handle assembly can also be configured to move thestylet proximally relative to a bone anchor assembly during insertion ofthe bone anchor assembly into bone. Such movement of the stylet canoccur automatically, in response to rotation of a portion of the handleto drive the bone anchor assembly into bone. Such a configuration isparticularly advantageous as it will prevent further insertion of thestylet into bone during advancement of the bone anchor assembly. Aperson skilled in the art will appreciate that the instruments disclosedherein can have a variety of configurations, and that the variousfeatures disclosed in the various embodiments are interchangeable.

FIGS. 2A and 2B illustrate one exemplary embodiment of a surgicalinstrument 100 for driving a bone anchor assembly into bone. Thesurgical instrument can include a handle assembly 106 having an elongateshaft 102 extending distally therefrom, and a stylet 104 extendingthrough the handle assembly 106 and the elongate shaft 102. The elongateshaft 102 can be configured to mate to a bone anchor assembly, and thehandle assembly 106 can be configured to both drive a bone anchorassembly into bone, and manipulate the stylet both before and duringinsertion of a bone anchor assembly into bone.

The elongate shaft 102 can have a variety of configurations, butgenerally the shaft 102 includes a proximal end 108 for coupling to thehandle assembly and a distal end 110 for mating to a bone anchorassembly. A length of the shaft 102 can vary, but the shaft preferablyhas a length sufficient to allow the handle assembly to be positionedoutside of a patient's body while the distal end 110 is positioned intoa patient's body adjacent to bone. To facilitate mating to a bone anchorassembly, the distal end 110 of the elongate shaft 102 can include amating feature 112 formed thereon. The mating feature 112 can be formedanywhere along the elongate shaft 102, such as the distal end 110, andit can be configured to engage a bone anchor assembly (e.g., bone anchorassemblies of the type described above with respect to FIGS. 1A-1B). Themating feature 112 can include a threaded portion 113 configured toengage corresponding threads formed in the receiver member of the boneanchor assembly. The mating feature 112 can also include a tip 124disposed distally of the threaded portion 113 and configured to engage adrive socket or a proximal surface of the bone anchor disposed withinthe receiver member. The tip 124 can have a diameter that is less thanthe diameter of the threaded portion 113. The mating feature 112 canalso be configured to engage a bone tap, or a bone tap can be formedintegrally with the elongate shaft 102. One or more bulges 126 or areasof increased diameter can be formed along the length of the elongateshaft 102 to engage and stabilize extension or protective sleeves thatcan be coupled to the bone anchor assembly. As shown in FIG. 2B, thebone anchor assembly can include break-off extensions 125, which can actas a delivery cannula during insertion of the set screw and can bebroken off at the end of the procedure.

The elongate shaft 102 can include a cannulated proximal portion havinga bore extending at least partially therethrough and one or more slotsformed therein that define opposed tabs 136. The slot(s) can extendthrough only a portion of the proximal portion such that the opposedtabs 136 are connected at their proximal ends, or the slots extendthrough the entire length of the proximal portion as shown in theillustrated embodiment. A person skilled in the art will appreciate thatthe slots can have any length as may be required to allow fortranslation of the carrier, discussed below. In the illustratedembodiment, the tabs 136 can have a generally cylindrical configurationand define a hollow generally cylindrical interior lumen for receiving acarrier. A distal end of each tab 136 can be mounted on and can extendfrom a mounting surface defined by a proximal flange 143 formed on theelongate shaft, and a proximal end of each of the opposed tabs 136 canmate with a distal end of the proximal handle 120 such that rotation ofthe proximal handle 120 is effective to rotate the elongate shaft 102.In particular, the proximal end of each tab 136 can be sized to bereceived within a distal end of the proximal handle 120, as discussedbelow, and can be fixedly mated thereto, e.g., using an adhesive,welding, threads, or any other mating feature. In an exemplaryembodiment, threads (not shown) are formed on an outer surface of theproximal end of the opposed tabs 136 for mating with correspondingthreads formed within the proximal handle 120. Where the tabs are notconnected, a support collar 138 can optionally be disposed within aproximal portion of the opposed tabs 136 to prevent inward radialmovement of the opposed tabs and to maintain the threaded connectionbetween the opposed tabs 136 and the proximal handle 120, as shown inFIG. 2B; however, one or more of a variety of features can be used toconnect any part of the elongate shaft 102, such as the opposed tabs136, to the proximal handle 120. In addition, although described hereinas opposed tabs 136, the proximal end of the elongate shaft 102 can havea variety of configurations including various shapes and sizes.Preferably, the proximal end is in the form of a body having a lumen andat least one slot, with the shape of the body varying as may bedetermined based on the shape of the handle disposed therearound. Anynumber of a variety of features and configurations can be included atthe proximal end of the elongate shaft 102 and are not limited toopposed tabs 136.

As indicated above, the handle assembly 106 can be located adjacent theproximal end 108 of the elongate shaft 102 and can include a proximalhandle 120 and a distal handle 122. The handle assembly 106 can bepositioned and sized to allow a user, such as a surgeon, to grasp a partof the handle assembly 106 and operate the surgical instrument 100.While the proximal and distal handles 120, 122 can each have a varietyof configurations, in the illustrated embodiment each handle 120, 122has a generally elongate cylindrical configuration and is cannulatedwith an inner lumen extending therethrough, as shown in FIG. 2B. Eachhandle 120, 122 can include gripping features, such as knurling or othersurface features, formed thereon to facilitate grasping of the device.The proximal handle 120 can be coupled to the proximal end 108 of theelongate shaft 102 and can be configured to rotate the elongate shaft102, such as to drive a bone anchor assembly coupled to the matingfeature 112 into bone. In particular, as described above, threads orother mating features on a proximal end of the opposed tabs 136 can mateto threads 147 formed within a distal portion of the inner lumen of theproximal handle.

As shown in FIG. 2B, the inner lumen in the proximal handle 120 includesan enlarged diameter region along its distal portion for receiving aproximal-most end or extension 145 of the opposed tabs 136 at theproximal end of the elongate shaft 102. The distal handle 122 can bepositioned just distal to the proximal handle 120 and can be moveablydisposed about a proximal portion of the elongate shaft 102. Inparticular, as shown in FIG. 2B, the distal handle 122 can be disposedabout the opposed tabs 136 of the elongate shaft 102 and can beconfigured to freely rotate relative to at least the elongate shaft 102.The proximal flange 143 on the elongate shaft 102 can assist inpreventing translational movement of the distal handle 122 relative tothe proximal handle 120 and elongate shaft 102. In order to facilitatemounting of the distal handle 122 about the opposed tabs 136, the innerlumen extending through the distal handle can have a diameter that isslightly larger than an outer diameter of the opposed tabs 136. Asfurther shown in FIG. 2B, the distal handle 122 can include interiorthreads 134 formed therein and extending along at least a portion or anentire length of the inner lumen extending through the distal handle122. The threads 134 can mate with threads on the carrier, as discussedbelow. In use, each of the proximal and distal handles 120, 122 can berotated relative to one other while the other handle is held stationary.Rotation of the proximal handle 120 will rotate the shaft 102 to drive abone anchor assembly into bone, and rotation of the distal handle 122can assist with positioning the stylet 104 relative to the elongateshaft 102, such as to allow a length of stylet 104 to extend from thedistal end 110 of the elongate shaft 102, as will be discussed in detailbelow.

Although described as the proximal handle 120 being configured to rotatethe elongate shaft 102 and the distal handle 122 being configured toaxially translate the stylet 104 relative to the elongate shaft 102, theproximal handle 120 can be configured to axially translate the stylet104 relative to the elongate shaft 102 and the distal handle 122 can beconfigured to rotate the elongate shaft 102.

Continuing to refer to FIGS. 2A and 2B, the surgical instrument 100 canfurther include a carrier 130 movably disposed within the handleassembly 106. The carrier 130 can be configured to couple to a stylet,as discussed below, and in use the carrier can facilitate positioning ofthe stylet relative to a bone anchor assembly coupled to the elongateshaft 102.

While the carrier 130 can have a variety of configurations, in theillustrated embodiment the carrier 130 has a generally cylindricalconfiguration and is cannulated with an inner lumen extendingtherethrough. As shown in FIG. 2B, the carrier 130 can be slidablydisposed within the opposed tabs 136. The carrier 130 can thus have anouter diameter that is less than an inner diameter of the lumen definedby the opposed tabs 136 to allow the carrier to be disposed therein. Thecarrier 130 can include one or more threaded features 132 formed on anouter surface of the carrier 130 that engage the interior threads 134located on an inner surface of the distal handle 122. As shown in FIG.2B, the carrier 130 includes first and second threaded features formedon opposed sides thereof and not extending fully circumferentiallyaround the carrier, with the opposed threaded features being receivedwithin the opposed slots 140 in the opposed tabs 136. Thus a portion ofthe outer surface of the carrier 130 can be non-threaded and configuredto slide along or adjacent the inner walls of the opposed tabs 136, suchas when the carrier 130 translates and moves the stylet 104 in aproximal or distal direction. The one or more slots 140 can allow theone or more threaded features 132 formed on opposed sides of the carrierto extend therethrough and to engage the threaded features 134 of thedistal handle 122. Such a configuration will allow the threaded features134, and thus the carrier 130, to translate axially along the opposedtabs 136, yet will prevent rotation of the carrier relative to theopposed tabs 136, and thus the elongate shaft 102. As a result, when theproximal handle 120 is be held by the user and the distal handle 122 isrotated, the threads 134 in the distal handle 122 will interact with thethreaded features 132 on the carrier 130 to cause the carrier 130 totranslate axially without rotating along the opposed tabs 136 andrelative to the elongate shaft 102. In addition, if the distal handle122 is held and the proximal handle 120 is rotated, the opposed tabs136, which rotate in coordination with the proximal handle 120, willforce the carrier 130 to rotate. The interaction between the threads inthe distal handle 122 and the threaded features 132 on the carrier willthus cause the carrier 130 to translate axially along the opposed tabs136 and thus relative to the elongate shaft.

In some implementations, the thread pitch of the carrier 130 and distalhandle 122 can be the same as the thread pitch of the bone screw. Thedirection of the threads in the carrier 130 and distal handle 122,however, are preferably reversed as compared to a direction of thethreads on a bone-screw. Such a configuration can allow the bone screwto advance into the bone at approximately the same rate as the stylet isretracted, as discussed below. Reversal of the thread pitch also resultsin a configuration in which the proximal handle 120 can be rotated in afirst direction, e.g., clockwise, to drive a bone screw into bone, whilerotation of the distal handle in a second opposite direction, e.g.counter-clockwise, is effective to advance the carrier 130 and styletdistally through distal handle 122. In other embodiments, the threadpitch of the carrier 130 and distal handle 122 can differ from thethread pitch of the bone screw so as to result in movement of the styletat a rate that is greater or less than a rate of insertion of the bonescrew. In addition, the slots 140 can extend approximately 30millimeters to approximately 60 millimeters. Thus, this can allow thecarrier 130 and stylet 104 to translate a distance of approximately 30millimeters to approximately 60 millimeters. However, the slots 140 canextend a variety of lengths and are not limited to the examplesdescribed herein.

Movement of the carrier 130 within the distal handle 122, as describedabove, can cause corresponding movement of a stylet coupled thereto.FIGS. 2A and 2B illustrate a stylet 104 having a generally elongateconfiguration with a pointed distal tip to facilitate insertion intobone. As noted above, the stylet 104 or guidewire can have a variety ofconfigurations. As shown in FIGS. 2A and 2B, the carrier 130 can includean inner lumen 144 that extends along the length of the carrier 130 andis configured to allow the stylet 104 to extend through. The stylet 104can be integrally formed on and can extend distally from the carrier130, or it can be removably mated to the carrier, such as with theassistance of a mating element (e.g., set screw). For example, themating element can allow the length of stylet 104 extending in adirection from the carrier 130 to be altered. In the illustratedembodiment, the carrier 130 can include a threaded thru-hole 146extending radially through a sidewall thereof that can accept a setscrew 142 that can be advanced into the carrier 130 in order to engageand secure the stylet 140 within the inner lumen 144 of the carrier.Additionally, the handle assembly 106, such as the distal handle 122,can include a thru-hole 148 that can allow a tool to be inserted throughthe thru-hole and to access the set screw for adjusting the axialposition of the stylet 104 relative to the carrier 130. For example,adjusting the position of the stylet 104 relative to the carrier 130 canaffect the length of stylet 104 that can extend from the distal end 110of a bone anchor assembly coupled to the elongate shaft 102. Forexample, distal translation of the stylet 104 can allow the length ofstylet extending from the distal end 110 of the elongate shaft 102 toincrease and proximal translation of the stylet 104 can allow the lengthof stylet 104 extending from the distal end 110 of the elongate shaft102 to decrease.

FIG. 3 illustrates an embodiment of a surgical instrument 200 fordriving a bone anchor assembly into bone that is identical to that ofFIGS. 2A and 2B, except that the stylet 204 is integrally formed withthe carrier 230. As shown in FIG. 3 , the stylet 204 is unitary ormonolithic with the carrier 230 and extends distally from a distal sideof the carrier 230. In this embodiment, the stylet 204 can translaterelative to the elongate shaft 202, but the stylet 204 cannot translaterelative to the carrier 230. As such, the maximum length of stylet 204that can extend from the distal end 210 of the elongate shaft 202 whenthe carrier 230 is in a most distal position relative to the distalhandle 222 cannot be adjusted (i.e., lengthened or shortened).

FIG. 4 illustrates another embodiment of a surgical instrument 300 fordriving a bone anchor assembly into bone. The instrument 300 of FIG. 4is identical to that of FIGS. 2A and 2B, except that the stylet 304 isthreadably engaged with the carrier 330. For example, the stylet 304 caninclude threads 350 along a proximal portion of the stylet 304. Inaddition, the carrier 330 can include a thru-hole 352, with at least apart of the thru-hole including threads that can threadably engage thethreads 350 along the stylet 304. Furthermore, the thru-hole 350 caneither have more than one diameter (e.g., a recessed bore) or not bethreaded all the way through, such as in order to prevent the stylet 304from advancing too far through the carrier 330 or becoming disengaged.As such, the proximal end of the stylet 304 can be passed through thethru-hole 352 of the carrier 330 and the threaded portion 350 of thestylet 304 can be threadably engaged with the carrier 330 until thestylet 304 is secured to the carrier 330. Once the stylet 304 is securedto the carrier 330, such as during manufacturing of the surgicalinstrument, the stylet 304 can translate relative to the elongate shaft302, but the stylet 304 cannot translate relative to the carrier 330. Assuch, the maximum length of stylet 304 that can extend from the distalend 310 of the elongate shaft 302 when the carrier 330 is in a mostdistal position relative to the distal handle 322 cannot be adjusted(i.e., lengthened or shortened).

FIGS. 5A-5G illustrate yet another embodiment of a surgical instrument400 for driving a bone anchor into bone. The instrument 400 of FIGS.5A-5G is identical to that of FIGS. 2A and 2B, except that the surgicalinstrument 400 includes a stylet holder 460 that can assist withcoupling a stylet 404 to a carrier 430. The stylet holder 460 caninclude a thru-hole 462 along the length of the stylet holder 460 andthe stylet 404 can extend through the thru-hole 462 in order to slidablyengage with or secure to a part of the thru-hole 462. The stylet holder460 can be loaded and/or removed from either the distal end or proximalend of the stylet holder. The engagement of the stylet 404 with thestylet holder 460 can depend on a positioning of the stylet holder 460relative to the carrier 430, as will be described in greater detailbelow.

The stylet holder 460 can have a generally cylindrical configuration,although an outer diameter can vary along external portions thereof. Asshown, the stylet holder 460 includes a proximal non-threadedcylindrical portion that is sized to be received within the supportcollar 438, and a distal portion having a threaded member 462 and aclamping feature 464. The distal portion is configured to be receivedwithin the carrier 430 such that the threaded member 462 formed along anouter surface of the stylet holder 460 is threadably engaged with athreaded bore 432 of the carrier 430. The clamping feature 464 is in theform of a slotted tapered nose defining opposed arms that arecompressible radially inward to engage the stylet. The arms taperradially inward toward the distal-most end.

In use, the stylet holder 460 can be movable between a first position(unlocked) and a second position (locked) relative to the carrier 430.For example, in the first position, the stylet holder 460 can be, atmost, partially threadably engaged with the carrier 430. In addition,when the stylet holder 460 is in the first position the clamping feature464 of the stylet holder 460 is not engaged with the carrier. When theclamping feature 464 of the stylet holder 460 is not engaged with thecarrier 430, the clamping feature 464 does not compress around thestylet 404 and allows the stylet 404 to be axially slidably moved withinthe stylet holder 460.

In the second position, the stylet holder 460 is fully threaded into thethreaded bore 432 of the carrier 430 such that the clamping feature 464of the stylet holder 460 is received within a tapered bore 434 formed inthe carrier 430. When the clamping feature 464 of the stylet holder 460is engaged with the tapered bore 434 of the carrier 430, the taperedbore 434 causes the arms of the clamping feature 464 to compress towardone another and around the stylet 404 such that the stylet holder 460rigidly engages the stylet 404, thereby preventing axial translation ofthe stylet 404 independent of the stylet holder 460.

The stylet holder 460 can be advanced into the carrier 430 by thethreaded engagement between the stylet holder 460 and the carrier 430.In addition, the stylet holder 460 can include a tool-engaging feature466 (e.g., a recessed hex feature) that can allow a tool (e.g., aprotruding hex feature) to engage and force the stylet holder 460 torotate, such as relative to the carrier 430. For example, the styletholder 460 can be forced to rotate in a first direction (e.g.,clockwise) relative to the carrier 430 in order to move the styletholder 460 to the second position. In addition, stylet holder 460 can beforced to rotate in a second direction (e.g., counterclockwise) relativeto the carrier 430 in order to move the stylet holder 460 to the firstposition.

FIGS. 5A-5C further illustrate a ring 463 disposed between the proximaland distal handles 420, 422. The ring can be utilized with any of theembodiments disclosed herein, and acts as a holder for a positioningdevice, such as a three-dimensional sensor array for use in facilitatingnavigation during a surgical procedure. As show, the ring 463 isgenerally annular in shape and includes a bore 465, e.g., a threadedbore, formed therein for mating with a positioning device.

FIG. 5D illustrates an embodiment of tool that can be used to adjust aposition of the stylet and to move the stylet holder between the firstand second positions. A person skilled in the art will appreciate thatthe illustrated tool can be used with any of the devices describedherein. As shown in FIG. 5D, the tool can include a positioning handle480 that is configured to mate to a proximal end of the stylet 404. Thepositioning handle 480 can allow a user to advance the distal end of thestylet 404 through the stylet holder 460, such as when the stylet holder460 is in the first position (i.e., the stylet 404 can translaterelative to the stylet holder 460). In addition, the distal end of thepositioning handle 480 can have a tool feature 482 (e.g., a protrudinghex feature) that can engage the tool-engaging feature 466 of the styletholder 460. As such, after advancing the stylet 404 through at least thestylet holder 460, the positioning handle 480 can engage thetool-engaging feature 466 of the stylet holder 460 and force the styletholder 460 to rotate relative to the carrier 430 and form the secondposition with the carrier 430 (i.e., the stylet holder 460 rigidlyengages the stylet 404).

As shown in FIGS. 5E-5G, the positioning handle 480 can include an outerbody 484 encompassing at least a part of a positioning feature 486. Thestylet 404 can extend from a distal end of the positioning feature 486and out through a distal end of the outer body 484. The positioningfeature 486 can include a push button 488 that can be depressed in orderto disengage the positioning feature 486 from the outer body 484 andallow the positioning feature 486 and stylet 404 to translate relativeto the outer body 484. As such, the positioning feature 486 can vary thelength that the stylet 404 extends from the positioning handle 480,which can also vary the length of stylet 404 that can extend distallyfrom the elongate shaft 402 (e.g., after the positioning handle 480 hascoupled the stylet 404 to the stylet holder 460). Although describedherein as a push button 488, any number of a variety of features fordisengaging the positioning feature 486 from the outer body 484 can beused, such as, for example, a sliding or threaded feature.

In some embodiments, the push button 488 can engage the outer body 484of the positioning handle 480 in a number of engagement positions 490.In addition, either the engagement positions 490 or the positioningfeature 486 can include markings 492 that can inform a user as to theapproximate length the stylet 404 extends from the elongate shaft 402based on the type (e.g., length) of bone anchor attached (or to beattached) to the elongate shaft 402. For example, the outer body 484 caninclude a window 494 that reveals one of a plurality of markings (e.g.,numbers) formed on the positioning feature 486. Each marking cancorrespond to a length of stylet 404 extending distally beyond adistal-most end of the elongate shaft 402. In addition, the markings cancorrespond to various bone anchor length to be used with the instrumentto allow a user to select an appropriate bone anchor and adjust thestylet 404 relative to the elongate shaft 402 based on the selected boneanchor. For example, the user can select a 45 millimeter bone anchor tobe implanted in a patient. The user can then set the positioning handle480 (e.g., by pushing the push button 488 and moving the positioningfeature 486) such that a marking (e.g., shown in the window 494)indicates that the stylet 404 is appropriately positioned relative tothe elongate shaft 402 or bone anchor for a 45 millimeter bone anchorattached to the surgical instrument 400. In this position, apredetermined length (e.g., approximately 1 millimeter to approximately30 millimeters) of the tip of the stylet 404 can extend distally beyonda distal-most end of the bone anchor mounted onto the elongate shaft402.

In addition, after the stylet 404 has been initially positioned relativeto the elongate shaft 402, the user can continue to observe thepositioning of the stylet 404 relative to the elongate shaft 402 andbone anchor mounted thereon. For example, while not shown, in someembodiments, the stylet holder 460 can include a proximal extension thatcan include markings corresponding to the length of stylet 404 extendingdistally beyond the elongate shaft 402 or bone anchor. Additionally, theproximal handle 420 can include one or more viewing windows 423 that canallow a user to view the markings along the proximal extension of thestylet holder 460 in order to determine the length of stylet 404extending from the distal end of the elongate shaft 402 or bone anchor.Although described herein as using markings, such as numbers, toindicate the stylet length to the user, any number of indicia, such ascolors, pictures, etc., can be used.

In use, when the stylet holder 460 is in the first position (unlocked),the user can manipulate the positioning feature 486 to cause the stylet404 to translate relative to the stylet holder 460 and along theelongate shaft 402, thereby adjusting a length of the stylet extendingfrom a bone anchor assembly coupled to a distal end of the elongateshaft 402. Rotation of the positioning handle 480 can thread the styletholder 460 into the carrier 430, thereby moving the stylet holder 460 tothe second position (locked). The positioning handle 480 can be removedand the stylet 404 can be released from the positioning handle 480, suchas due to a sliding or snap fit between the positioning handle 480 andstylet 404.

FIGS. 6A and 6B illustrate another embodiment of a surgical instrument500 for driving a bone anchor assembly into bone. The surgicalinstrument 500 can include an elongate shaft 502, a stylet 504, and ahandle assembly 506. The elongate shaft 502 can have a proximal end 508and a distal end 510, with a mating feature 512 formed on the distal end510 and configured to mate to a bone anchor assembly. The elongate shaft502 can be hollow with an inner lumen that can extend through and alongthe length of the elongate shaft 502. The stylet 504 can extend throughat least a part of the elongate shaft 502, such as the inner lumen.

The handle assembly 506 can be coupled to a proximal end 508 of theelongate shaft 502 and can include a proximal handle 520 and a distalhandle 522. The handle assembly 506 can be positioned and sized to allowa user, such as a surgeon, to grasp a part of the handle assembly 506and operate the surgical instrument 500. In this embodiment, the handlesare reversed as compared to prior embodiments. In particular, theproximal handle 520 controls a position of the stylet, whereas thedistal handle 522 is used for driving a bone anchor assembly into bone.

As shown, the distal handle 522 is positioned between the proximalhandle 520 and the proximal end 508 of the elongate shaft 502. Thedistal handle 522 has a proximal portion with a reduced diameter regionthat allows the proximal portion to be received within a bore 525 formedin the proximal handle 520. The proximal portion can include threads 592formed on an external surface thereof that engage with correspondingthreads 590 formed within the bore 525 extending proximally into adistal end of the proximal handle 520. The distal portion of the distalhandle 522 is enlarged to facilitate grasping, and includes a bore 527formed in a distal-most end thereof for receiving a proximal end 508 ofthe elongate shaft 502. As a result, rotation of the distal handle 520relative to the proximal handle 520 will rotate the elongate shaft 502.As further shown, the bore 525 formed in proximal handle 520 includes areduced diameter region 529 at a proximal-most end thereof for matingwith a stylet 504. The stylet 504 can be threadably mated within thereduced diameter region 529, or otherwise fixedly mated thereto. Assuch, rotation of the proximal handle 520 relative to the distal handle522 can translate the stylet 504 in a proximal or distal directionrelative to the elongate shaft 502. Furthermore, rotation of the distalhandle 522 can rotate the elongate shaft 502.

A mating feature 512 can be formed at the distal end 510 of the elongateshaft 502 and can be configured to engage a bone anchor assembly (e.g.,bone anchor assemblies of the type described above with respect to FIGS.1A-1B). The mating feature 512 can include a threaded surface configuredto engage corresponding threads formed in the receiver membrane of thebone anchor assembly. The mating feature 512 can also include a tip 524disposed distally of the threaded surface configured to engage a drivesocket or a proximal surface of the bone anchor or a compression cap(not shown) disposed within the receiver member. The tip 524 can have adiameter that is less than the diameter of the threaded portion. Themating feature 512 can also be configured to engage a bone tap, or abone tap can be formed integrally with the elongate shaft 502. One ormore bulges 526 or areas of increase diameter can be formed along thelength of the elongate body to engage and stabilize extension orprotective sleeves that can be coupled to the bone anchor assembly.

In use, the stylet 504 can translate along a length of the inner lumenof the elongate shaft 502 and can extend out from the distal end 510 ofthe elongate shaft 502. In addition, translation of the stylet 504 alongthe inner lumen can allow the length of stylet 504 that extends from thedistal end 510 of the elongate shaft 502, and in particular from adistal end of a bone anchor assembly coupled to the elongate shaft, tovary. For example, distal translation of the stylet 504 can allow thelength of stylet extending from a bone anchor assembly to increase andproximal translation of the stylet 504 can allow the length of stylet504 extending from a bone anchor assembly to decrease. When the proximalhandle 522 is fully threadably engaged, as shown in FIG. 6B, the styletis fully extended from the bone anchor assembly and is at its maximumlength.

FIG. 7 illustrates an embodiment of a protective sleeve 600 positionedover a part of an elongate shaft of a surgical instrument, such as theelongate shaft 502 of surgical instrument 500 described above and shownin FIGS. 6A and 6B. The protective sleeve 600 can assist withneurotransmitting procedures, such as neuromonitoring navigation. Theprotective sleeve can act as an insulator that can insulate at least thestylet. By way of non-limiting example the protective sleeve can beformed from one or more of a radio-opaque and radiolucent material, andcan include radiopaque markers.

FIG. 8 illustrates another embodiment of a protective sleeve 600positioned over a part of an elongate shaft of a surgical instrument,such as the elongate shaft 302 of surgical instrument 300 describedabove and shown in FIG. 4 . Although the protective sleeve 600 is shownand described as being coupled to the surgical instruments 300 and 500shown in FIGS. 7 and 8 , any number of surgical instruments, includingany disclosed herein, can be coupled with the protective sleeve 600.

Methods

The various instruments disclosed herein can be used to perform avariety of surgical procedures. While exemplary methods are discussedbelow for delivering a bone screw to a vertebra, a person skilled in theart will appreciate that the instruments can be used to deliver avariety of implants in various surgical procedures. By way ofnon-limiting example, the instruments can be used to deliver screws tosoft tissue or bone throughout a patient's body, in minimally invasive,arthroscope, endoscopic, open, or other surgical procedures.

FIGS. 9A-9C schematically illustrate one exemplary methods of using asurgical instrument having a stylet to drive a bone anchor assembly intobone 824. The method detailed below can be used with any of theinstruments disclosed above (e.g., the instruments 100, 200, 300, 400),with any necessary modifications being apparent to one skilled in theart having read the above disclosure. By way of example, the method isdescribed in connection with instrument 100 of FIGS. 2A-2B.

To begin with, an incision can be made to access the bone 824 (e.g., avertebra) to which the bone anchor assembly 900 (e.g., a pedicle screw)is to be coupled. The bone anchor assembly 900 can be coupled to theinstrument 100 and advanced through the incision to position the boneanchor assembly in proximity to the bone surface. Prior to, during, orafter insertion into through the incision, the stylet 104 can be indexedto an initial position based on various parameters such as the length ofthe bone anchor assembly. This can be accomplished, for example, byrotating the distal handle 122 while holding the proximal handle 120fixed, to cause the carrier 130 and corresponding stylet 104 totranslate axially. In other embodiments, for example using theinstrument of FIGS. 4-5G, the stylet can be axially slid relative to thestylet holder prior to locking the stylet to the stylet holder. In someembodiments, the stylet 104 can be initially positioned such that thestylet 104 protrudes from the distal end of the bone anchor assembly 900by a desired amount. This can be achieved, for example, using thepositioning handle 480 (e.g., by pushing the push button 488 and movingthe positioning feature 486) such that a marking (e.g., shown in thewindow 494) indicates that the stylet 404 is appropriately positionedrelative to the elongate shaft 402. For example, the positioning handle480 can be set to display a marking that corresponds to a length of theselected bone anchor, such that a predetermined portion of the tip ofthe stylet extending distally beyond a distal end of the bone anchorattached to the surgical instrument 400. The length can be furtheradjusted by adjusting the stylet relative to the carrier as may bedesired. It will be appreciated that the stylet 104 can be initiallypositioned such that the stylet 104 does not protrude from the distalend of the bone anchor assembly 900.

As shown in FIG. 9A, the protruding stylet 104 can be docked into thepedicle 822 by tapping or urging the instrument distally towards thebone surface. The distal handle 122 can be rotated relative to theproximal handle 120, e.g., in a clockwise direction, in order to causethe stylet 104 to mechanically advance into the bone, as shown in FIG.9B. Alternatively, or in addition, an impact force can be applied to thestylet 104 in the distal direction to advance the stylet 104 into thebone. The proper trajectory and depth can be confirmed with fluoroscopy.The insertion depth can also be inferred by the surgeon (e.g., based onthe number of rotations of the distal handle 122, audible or tactilefeedback, visual feedback provided by graduations or markings, such asshown through the viewing window 423 of the proximal handle 420, orbased on the carrier hitting a stop disposed in or on the surgicalinstrument).

Once the stylet 104 is advanced to the desired depth, the proximalhandle 120 can be rotated, e.g., in a clockwise direction, relative tothe distal handle 122 (i.e., the distal handle 122 is held fixed) inorder to drive the bone anchor assembly 900 along the path created bythe stylet 104, as shown in FIG. 9C. Referring back to FIGS. 2A and 2B,rotation of the proximal handle 120 while holding the distal handlefixed 122 will cause corresponding rotation of the opposed tabs 136 onthe proximal end of the elongate shaft 102. Since the carrier 130 iskeyed to the tabs 136, the carrier 130 will be caused to rotate incoordination with the tabs 136. As a result, the threaded features 132on the carrier will rotate relative to the threads 134 formed in thedistal handle 122, which is held stationary. The carrier 130 will thusbe forced to translate along the opposed tabs 136. Since the threads arereversed as compared to the threads on the bone screw, the carrier 130will move proximally within the distal handle 122, thus moving thestylet 104 in a proximal direction relative to the bone screw 900. Sincethe stylet 104 is held fixed against the bone, the stylet 104 can bemaintained at a constant depth within the bone as the bone anchorassembly 900 is advanced distally over the stylet 104. The handleassembly will move distally along the stylet 104 in coordination withdistal advancement of the bone anchor assembly 900. In embodiments inwhich the threaded features of the carrier 130 and distal handle 122have the same pitch as the threaded portion of the bone anchor assembly,retraction of the stylet 104 into the bone anchor assembly 900 can occurat the same rate as the advancement of the bone anchor assembly 900,such that the stylet 104 remains at a substantially fixed depth withinthe bone. In embodiments in which the threaded features of the carrier130 and distal handle 122 have a smaller pitch than the threaded portionof the bone anchor assembly, retraction of the stylet 104 into the boneanchor assembly 900 can occur at a slight faster rate than advancementof the bone anchor assembly 900, such that the stylet 104 is at leastpartially retracted in a proximal direction relative to the bone as thebone anchor is driven into bone.

When the bone anchor assembly 900 is driven to the desired depth, thestylet 104 and the elongate body 102 can be detached from the boneanchor assembly and removed from the incision. Subsequent steps, such asaffixing a spinal rod or other component to a receiver member of thebone anchor assembly can then be performed.

The bone anchor assembly can include various self-tapping features tofacilitate insertion into the bone and to prevent the bone fromfracturing during anchor insertion. In some instances, patient anatomyor surgeon preferences can require the bone to be tapped beforeinserting the bone anchor assembly. In such instances, the above methodcan be modified to use embodiments of the surgical instrument thatinclude an integral bone tap or which are coupled to a bone tap via theengagement portion.

As discussed above, a tool can be used to adjust the position of astylet of an instrument with respect to either an elongate shaft of theinstrument or a bone anchor assembly coupled to the elongate shaft. Asshown in FIGS. 5D-5G, the tool can include a positioning handle 480,which can be used to adjust the position of the stylet 404 relative toan elongate shaft, such as the elongate shaft 402 of the instrument 400embodiment shown in FIGS. 5A-5D. Although the positioning handle 480 isdescribed herein with respect to the instrument 400 embodiment shown inFIGS. 5A-5D, the positioning handle 480 can be used with any of theinstrument embodiments.

FIGS. 10A-10D schematically illustrate another exemplary method of usinga tool or positioning handle 480 with the surgical instrument 400 havinga stylet 404 to drive a bone anchor assembly 900 into bone 824. To beginwith, a distal end of the positioning handle 480 can be removablycoupled to a proximal end of the stylet 404, as shown in FIG. 10A. Thelength of stylet 404 extending from the elongate shaft 402 of theinstrument 40 can be adjusted by pressing the push button 488 andsliding the positioning feature 486 in a distal direction (e.g., toincrease the length) or proximal direction (e.g., to decrease thelength). Once the stylet 404 length has been set (i.e., the push buttonis released and engages an engagement position 490), the user can engagethe tool feature 482 at the distal end of the positioning handle 480into the tool-engaging feature 466 of the stylet holder 460 in order torotate the stylet holder 460. The stylet holder 460 can be rotatedrelative to the carrier 430 until the stylet holder 460 forms the secondposition with the carrier 430 where the stylet holder 460 rigidlyengages the stylet 404 and locks the position of the stylet 404 relativeto at least the stylet holder 460. The user can then remove thepositioning handle 480 from the stylet 404 (e.g., pull the positioninghandle 480 off the proximal end of the stylet 404).

The distal end of the instrument 400 can then be inserted into theincision and the distal end of the stylet 404 can be docked against thebone. The user can then apply a distally directed force on the proximalend of the instrument 400 in order to force the stylet 404 into thebone. Alternatively or in addition, the user can hold the proximalhandle 420 and rotate the distal handle 422 in order to force the stylet404 in the distal direction and into the bone. Once a desired length ofstylet 404 has engaged the bone, the user can then rotate the proximalhandle 420 in order to drive the bone anchor assembly 900 into the bone.

Alternatively, the bone anchor assembly 900 may not have been attachedto the distal end of the elongate member 402 prior to insertion of thedistal end of the instrument into the incision. A tool (e.g., having aprotruding hex feature) can be inserted into the tool-engaging feature466 (e.g., having a recessed hex feature) of the stylet holder 460 inorder to rotate the stylet holder 460 relative to the carrier 430 andposition the stylet holder 460 in the first position. As describedabove, when the stylet holder 460 is in the first position, the stylet404 can move relative to the stylet holder 460. Therefore, the stylet404 can remain in place (e.g., inserted into the bone) and the remainderof the surgical instrument 400 can be slid off the proximal end of thestylet 404, as shown in FIG. 10B. Such a configuration allows variousother procedures to be performed at the surgical site withoutinterference from the instrument 400, while at the same time maintainingthe position of the stylet. Once the site is ready for anchorimplantation, a user can attach a bone anchor assembly 900 onto thedistal end 410 of the elongate member 402. Once the bone anchor assembly900 is attached, the user can lead the proximal end of the stylet 404through the distal end of the bone anchor assembly 900 and continue toadvance the surgical instrument along the stylet 404 until the distalend of the bone anchor assembly 900 is in contact with the bone, asshown in FIGS. 10C and 10D. The stylet holder 460 can then bere-positioned into the second position (e.g., using the tool) in orderto secure the stylet 404 to the stylet holder 460. The user can thenproceed with driving the bone anchor assembly 900 into the bone over thestylet 404 (e.g., rotating the proximal handle 420), as described above.

When the bone anchor assembly is driven to the desired depth, the stylet404 and the elongate body 402 can be detached from the bone anchorassembly 900 and removed from the incision. Subsequent steps, such asaffixing a spinal rod or other component to a receiver member of thebone anchor assembly 900 can then be performed.

It should be noted that any ordering of method steps implied by thedrawings or description herein is not to be construed as limiting thedisclosed methods to performing the steps in that order. Rather, thevarious steps of each of the methods disclosed herein can be performedin any of a variety of sequences. In addition, as the described methodsare merely exemplary embodiments, various other methods that includeadditional steps or include fewer steps are also within the scope of thepresent invention.

The stylet of the various embodiments disclosed herein can be rigid orflexible. The stylet can be formed from a radiopaque material tofacilitate visualization under fluoroscopy and other imaging techniques.Other components of the devices disclosed herein (e.g., elongate bodyportions, handle portions, and the like) can be formed from aradiolucent material so as not to interfere with visualization of theguide projection. Exemplary radiolucent materials include carbon fiberand high-strength polymers. The devices disclosed herein can also becompatible with image-guide surgical systems and with stimulationsystems (e.g., neuromonitoring systems typically used to monitor forpedicle breach and to confirm screw or instrument placement).

The methods and devices disclosed herein can provide a number ofadvantages. For example, in some embodiments, the time required totarget and place the bone anchor assembly can be reduced, the radiationexposure to the patient and to the surgical staff can be reduced, andprocedural steps such as needle placement, guidewire insertion andremoval, and tapping can be eliminated. By way of further example, insome embodiments, inadvertent advancement of instrumentation can beeliminated by controlling the guide projection depth throughout theprocedure, risk of removing a guidewire during removal of a needle ortap can be eliminated, and bending or kinking of a guidewire can beprevented.

The devices and methods disclosed herein can be used inminimally-invasive surgery and/or open surgery. While the devices andmethods disclosed herein are generally described in the context ofadvancing a bone anchor into a pedicle, it will be appreciated that themethods and devices disclosed herein can be used with any human oranimal bone, implant, non-living object, and so forth.

Although the invention has been described by reference to specificembodiments, it should be understood that numerous changes may be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedescribed embodiments, but that it have the full scope defined by thelanguage of the following claims.

What is claimed is:
 1. An instrument for driving a bone anchor intobone, comprising: an elongate shaft having a distal tip configured tocouple to a bone anchor; a handle assembly coupled to a proximal end ofthe shaft, the handle assembly including a first handle and a secondhandle; a stylet extending through an inner lumen that extends at leastthrough the first handle and the elongate shaft; and a carrier moveablycoupled to the handle assembly, wherein rotation of the first handlewhile the elongate shaft is stationary causes the carrier tonon-rotatably translate relative to the elongate shaft to cause thestylet to axially translate relative to the elongate shaft, and whereinrotation of the second handle causes the carrier to rotatably translateand causes rotation of the elongate shaft to advance the bone anchoralong the stylet.
 2. The instrument of claim 1, wherein the rotation ofthe second handle causes the carrier to rotate relative to the firsthandle.
 3. The instrument of claim 1, wherein the rotation of the secondhandle causes the carrier and the elongate shaft to rotate together. 4.The instrument of claim 3, wherein rotation of the second handle whilethe first handle is held stationary causes rotation of the elongateshaft and causes rotation and axial translation of the carrier withinthe second handle.
 5. The instrument of claim 1, wherein rotation of thefirst handle while the second handle is held stationary causes thecarrier to non-rotatably translate without rotating the elongate shaft.6. The instrument of claim 1, wherein the second handle is mated to theproximal end of the elongate shaft, and the first handle is rotatablydisposed about a proximal portion of the elongate shaft at a locationdistal to the proximal handle.
 7. The instrument of claim 1, furthercomprising a stylet holder having the stylet extending therethrough. 8.The instrument of claim 1, wherein the elongate shaft includes aproximal portion with at least one slot extending therealong, theproximal portion extending through the first handle and having aproximal end mated to the second handle.
 9. The instrument of claim 8,wherein the carrier is slidably disposed within the proximal portion,and the carrier is non-rotatable relative to the proximal portion suchthat the carrier and the elongate shaft rotate together.
 10. Theinstrument of claim 8, wherein the carrier includes one or more threadedfeatures that extend through the at least one slot, the at least oneslot allowing translation while preventing rotation of the carrierwithin the proximal portion of the elongate shaft.